package udpEcho;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

public class UdpEchoServer {
    private DatagramSocket socket = null;

    public UdpEchoServer(int port) throws SocketException {
        socket = new DatagramSocket(port);
    }

    public void start() throws IOException {
        //启动服务
        System.out.println("UdpEchoServer start");
        while (true) {
            //1.读取请求并解析
            DatagramPacket requestPacket = new DatagramPacket(new byte[4096], 4096);
            socket.receive(requestPacket);
            String request = new String(requestPacket.getData(), 0, requestPacket.getLength());
            //2.根据请求计算响应
            String response = process(request);
            //3.把响应返回给客户端
            DatagramPacket responsePacket = new DatagramPacket(response.getBytes(), response.getBytes().length, requestPacket.getSocketAddress());
            socket.send(responsePacket);
            //4.打印一个日志
            System.out.printf("[%s:%d] req:%s resp:%s\n", requestPacket.getAddress().toString(), requestPacket.getPort(), request, response);
        }
    }

    //后续如果要写别的服务器，只修改这里就好了
    private String process(String request) {
        return request;
    }

    public static void main(String[] args) throws IOException {
        UdpEchoServer server=new UdpEchoServer(9090);
        server.start();
    }
}
